Separation methods such as centrifugation and filtration have been used for a long time. Centrifugation is often a suitable method for thickening a liquid-solid mixture or for removing unwanted particles from a liquid-solid mixture before further use or treatment. Separation may also be carried out to avoid unwanted environmental problems or fire hazards.
U.S. Pat. No. 3,152,078 discloses a stationary-walled centrifuge for separating phases, especially for removing water and/or sand from crude petroleum oil. This centrifuge provides for high volume throughput and thus short retention time. However, U.S. Pat. No. 3,152,078 is silent on monitoring a production process from which a sample is withdrawn for subsequent analysis.
Filtration has been particularly used in the separation of wood fibre and filler materials from a paper furnish. However, it has not been possible to separate filler material and fibre fines from colloidal components due to the similar particle sizes. Furthermore, it has been shown that colloidal components tend to be retained in the fibre mat (cake) formed on the filter. Filtration devices are also often prone to fouling and require regular cleaning.
The intention of the present invention is to provide a convenient, inexpensive system monitoring a liquid fluid mixture which may be e.g. a process stream withdrawn from a production process, a tank containing e.g. a pulp suspension or the like, or monitoring at least one component in the liquid fluid mixture while avoiding the drawbacks of the prior art. Particularly, the invention intends to provide a system for monitoring a production process, e.g. a papermaking process. A further object of the invention involves providing a worked-up sample in which characterisation and measurements can be accurately performed in the substantial absence of separated interfering substances that would otherwise make the measurements less accurate. The invention further involves a method of optimally running a production process, particularly a paper-making process.